Harbor Seal

Range:

Habitat:

Live in temperate coastal habitats and haul out on rocks, reefs, beaches, and drifting glacial ice.

Characteristics:

Pacific harbor seals have spotted coats in a variety of shades from white or silver-gray to black or dark brown. They have glands in the skin that secretes oil which helps waterproof the hair. Harbor seals are true or crawling seals, having no external ear flaps. True seals also have small flippers.

The fore-flippers, or pectoral flippers, have all the major bones of the forelimbs of land mammals, but they are foreshortened and modified. The flippers are webbed and the fore-flippers have noticeable claws that the seals use for grooming, scratching, traction and defense.

Like land mammals, seals have five bony digits in the hind, or pelvic, limbs. The hind flippers also have claws, are webbed and are covered with hair. To swim the seals move their hind flippers side-to-side to propel themselves in water. The hind flippers also function as a rudder. They cannot rotate their hind flippers underneath their bodies like a sea lion and must move on land by flopping along on their bellies. This behavior makes them look a bit like a giant caterpillar.

Harbor seals have 34 to 36 teeth. The front teeth are pointed and sharp, adapted for grasping and tearing. They do not chew their food. Harbor seals often use their semi-flattened back teeth for crushing shells and crustaceans. Like sea lions whiskers called vibrissae grow from the thick pads of the seals upper lips and cheeks. Each is attached to muscle and supplied with blood and nerves. These sensitive whiskers grow throughout the seals lives and pick up vibrations in the water. This helps them to find food and avoid predators.

Behavior:

Unlike most other pinnipeds, harbor seals are generally solitary and rarely interact with one another outside of the breeding season. They maintain several feet of space between seals, even when hauled out on land. If touched by another harbor seal, they respond by growling, snorting, flipper-slapping and even biting.

Pacific harbor seals spend about half their time on land and half in water. Studies show that, within a season, harbor seals tend to return to one or two particular haul-out sites with regularity. The preferred sites may change seasonally.

Harbor seals can dive to depths of over 650 feet and search for food without surfacing for up to 30 minutes, although their average dive lasts three to seven minutes and is typically shallow.

While harbor seals swim safely in the surf, they will often watch humans walking on beaches. However, they are wary of people while on land and will rush into the water if approached too closely or disturbed. In fact, if disturbed too often, they have been known to abandon favorite haul-out sites or their pups.

Reproduction:

Mating season generally occurs in late spring through fall, when females come into season roughly six weeks after their pups are born. Prior to the pupping season, males and females exhibit pre-mating courtship that includes rolling, bubble-blowing, and mouthing each others necks. This pre-mating behavior ends with the beginning of the pupping season. Once the females give birth, the couples reunite and mating usually takes place in the water. Males will breed with several females.

Harbor seals have a total gestation of about 9 to 11 months. After breeding the fertilized egg enters a period of delayed implantation. The blastocyst stops growing and remains free-floating in the uterus for up to three months. It then implants on the uterine wall and continues to develop.

Delayed implantation gives the mother time to recover from her last pregnancy. It also assures that the next pup will be born at the same time the next year. This is when the habitat conditions are best for its survival.

Most pups are born in February through July depending on their latitude. Those further south are generally born earlier in the season than those to the north. Those born in British Columbia could be born as late as September.

Females generally give birth to one pup each year either on land or in the water. Twins are extremely rare. Unlike sea lion pups, seals can swim at birth. Pups range in size from 30 to 39 inches and weigh up to 26 pounds.

Unlike most seals, which fast while nursing, harbor seal mothers leave their pups during the nursing period to forage at sea. Researchers believe they may do this because their relatively small body size cannot store enough fat to withstand a fast.

On average, harbor seal milk is about 45% fat, 9% protein, and 45.8% water. On the fat rich milk, the pups more than double their weight by the time they are weaned. Pups may nurse on land or in the water for about a minute every four hours or so for four to six weeks.

Harbor seal mothers are attentive mothers and recognize their pups by vocalizations and by smell. However, once the pup is weaned it is on its own and she no longer pays attention to it. The pup will stay near other adults as it learns to forage. Once weaned the pup eats crustaceans such as shrimp and crabs and then learns how to catch fish.

Interesting Facts:

• Pups shed a white coat called lanugo shortly before or after birth. They do not molt again until they are a year old.

• Based on observations in zoos, harbor seals often decrease their food intake during molting.

• In the water they often sleep at the surface. They bob at the surface in a posture called bottling - their entire bodies remain submerged with just their heads exposed. This makes it easier to breathe when necessary. They will also sleep below the surface and on land.

• Harbor seals return to the same beaches year after year to give birth.

About Our Animals:

The Zoo currently is home to one male and two female harbor seals.

Conservation:

Worldwide, the harbor seal population is estimated at 500,000 individuals. They are not considered an endangered or threatened species. However, they do face threats by humans. Spring brings harbor seal colonies to rookery, or birthing beaches, that are accessible to humans.

Seal mothers often leave their pups on the beach while they return to the ocean to feed. Sometimes a pup and mother become separated due to disturbance by beach goers. This severely reduces the pup's chance for survival as the pups are highly susceptible to disease and stress and may not survive human encounters. The mother may also choose to abandon her pup if she feels threatened. Harbor seals are marine mammals and are protected by the Marine Mammal Protection Act. It is illegal to harass, touch or harm a harbor seal.

Another threat to harbor seals is discarded plastic and other human debris. They are curious and will often approach trash in the ocean and become entangled in it. Young seals may mistake it for food and eat it which can make them sick. Help keep all wildlife safe by putting trash where it belongs!

Did YOU Know?

A two-day-old harbor seal pup can stay submerged for up to two minutes.